1. Field of the Invention
The invention relates to a process and apparatus for fluid catalytic cracking a hydrocarbon feedstock which has been exposed to microwave energy. More particularly, the present invention relates to a process for fluid catalytic cracking a residuum which has been exposed to microwave energy prior to contact with fluid catalytic cracking catalysts.
2. Discussion of the Prior Art
In known and conventional catalytic cracking processes, a hydrocarbon feedstock, such as gas oil, is cracked in an elongated reactor riser, at elevated temperatures to provide a mixture of lighter hydrocarbon products. Suitable cracking catalyts include large pore crystalline zeolites, such as zeolite X or Y, and intermediate pore crystalline zeolites, such as ZSM-5. The products of the reaction, together with catalysts, are discharged into a separator located within an elongated stripping vessel, with the spent catalyst flowing downwardly therein. Prior to transfer to a catalyst regenerator unit, entrained hydrocarbon product is removed from the spent catalyst by means of a stripping gas, such as steam or nitrogen. Following regeneration, the catalyst is reintroduced into the riser to participate in another cycle of operation. Fluid catalytic processes are described in U.S. Pat. Nos. 3,617,497 to Bryson et al and 4,219,407 to Haddad et al.
Microwaves have been employed to heat hydrocarbon streams. U.S. Pat. No. 4,230,448 to Ward et al discloses an oil burner having a microwave energy source connected to a fuel supply line to heat the fuel.
U.S. Pat. No. 4,279,722 to Kirkbride discloses subjecting hydrocarbon reactants in contact with catalytic material, such as fluid catalytic cracking catalysts, with microwaves.
It would be desirable to provide a fluid catalytic cracking process which benefits from microwave energy but does not apply the microwave energy to hydrocarbons when the hydrocarbons contact catalysts.